Call ABI attributes on callee parameters vs call arguments

In https://reviews.llvm.org/D101806 we are going to change call lowering to only inspect the call arguments for ABI attributes, ignoring the callee parameter ABI attributes (if the call is a direct call).

The frontend should already properly be setting the call arguments’ ABI attributes, especially due to indirect calls where we can’t look at a callee’s parameter ABI attributes.

This is in line with 1 where we can’t prevent mismatched calling conventions.

I believe GlobalISel also needs to be fixed to do the same in CallLowering::getAttributesForArgIdx().

Are there any concerns?